An insulated gate bipolar transistor (IGBT) is a switching transistor used to permit power flow in when it is on and to stop power flow when it is off. It is a solid-state device and has no physical moving parts. Instead of opening and dosing a physical connection, the IGBT is operated by applying voltage to a semiconductor component, which changes its properties to create or block an electrical path. IGBTs are commonly used as switches, e.g. in chopper and frequency converter applications, to control and convert electrical power by switching electrical devices on and off at predetermined instances.
IGBT may either be used singly or connected in series. Generally, series operation of IGBTs is considered as a straightforward method to be used in high voltage power conversion. Failure of any one IGBT located in the series string of the IGBTs may result in the abnormal operation of the overall series-connected IGBTs, and even worse the overall IGBT phase legs may be damaged. For example, failure of any one IGBT in the series string may cause voltage unbalance issues and thus affect the robustness and reliability of the overall series-connected IGBTs. Therefore, it is desirable to achieve fast and accurate fault detection, including the fault type as well as the location for the failed IGBT among series-connected IGBTs.